Boiler control system



Dec. 8, 1931. C, B, PAGE ET AL 1,835,611

BOILER CONTROL SYSTEM 4 Filed Aug. 9, 1929 Char/60.5. Page Ernest WPGdde/so/z.

Patented Dec. 8, 1931- UNITED STATES PATENT OFFICE CHARLES B. PAGE, F EVANSTON, AN'D ERNEST W. REDDERSON, OF CHICAGO, ILLINOIS, ASSIGNORS, BY MESNE ASSIGNMENTS, T0 THE G. W. DULANY TRUST, 0F CHICAGO,

ILLINOIS, A COMMON LAW TRUST BOILEB CONTROL SY STEM Application filed August 9, 1929. Serial No. 384,764. i

The present invention relates to im rovements in control systems for gas-red oilers and water heaters. f

A n Iimportant object of the present invention resides in the provision of a novel control system in which the supply of gas to both a main burner and a ilot burneris automatically controlled by t e supply of air to said burners.

A more specific object of the invention resides in the provision of a control system comprising a main burner, a pilot burner, a proportional air and gas mixer for supplying a combustible mixture to the main burner, means for supplying air under pressure to the mixer, a line for supplying `gas to the mixer, means for supplying air under -pressure tothe pilot burner, a line for supplying gas to the pilot burner, an automatic valve in the gas line to the mixer responsive to the. supply of air to the mixer for controlling the supply of gas, an automatic valve in the gas line to the pilot burner responsive to the supply of air to the pilot burner for controlling the supply of as.

A further o ject resides in the provision in a control system of the foregoing character of automatic means responsive to the pressure in the boiler for regulating the supply of air to the mixer.

Still another object resides in the general combination making up the control system, said combination including various safety devices individually operable to stop the supply of air and as to the main burner, for example, when t e pressure exceeds a predetermined value, when the water lever falls below a predetermined minimum, and operable to stop completel the supply of air and gas both to the main urner and pilot burner should there be a suilicient drop in the gas main pressure or failure of gas supply which Would'endanger extinguishing the pilot burner.

Further objects and advantages will become apparent as the description proceeds.

In the accompanying drawing, the figure is a diagrammatic representationof a control system embodying the features of our invention.

While the invention is susceptible of various modifications and alternative constructions, We have shown in the drawing, and will herein describe in detail the preferred embodiment, but it is to be understood that we do not thereby intend to limit the invention to the specific form disclosed, but intend to cover all modifications and alternative constructions falling within theV spirit and scope of the invention as expressed in the appended claims.

Referring more particularly to the drawing, the control system may be applied to any suitable type of gas-tired boiler or Water heater. In the present instance, we have shown diagrammatically a vertical fire tube boiler 10, having an outer shell 11, an annular Water leg 12, a bottom tube sheet 13, a top tube sheet 14, vertical fire tubes 15 extending between and fastened to the top and bottom tube sheets, and a iiue gas outlet 16. Normally the water level is maintained at the aproximate level of the line 17, the space above this level constituting a steam space 18.

The boiler l0 is mounted on a suitable 'base structure having a casing consisting of a side wall 19, an inwardly extending top flange 20, and a bottom Wall 21. The top flange 20 conforms in size and shape to the annular Water leg 12 of the boiler 10 and constitutes a rigid support for the boiler. The side Wall 19 has a heat insulating lining 2:2, and the bottom Wall 21 has a heat insulating lining r23. The side wall 19 and the bottom Wall Q1 are further lined with a refractory lining 24, the refractoryv lining at the sides extendinnr above the top flange 20 and lining the insidie of the annular water leg 12 for a substantial distance above the top Harige 20 of the casing of the base structure.

The refractory lining 24, the Water legs 12 and the bottom tubesheet 13 form a closed combustion chamber 25. A suitable main yburner 26 is inserted in anbpenin through 95 A pilot burner 27 for ignitin-g the mainburner 26 is inserted through an opening in the side wall 19 and the heat insulating lining 22 and refractory lining 24. l The main burner 26 is connected through a fuel line 28 to a suitable proportional mixer 29. Preferably, this mixer is of the type in which a jet of air, adjustable in volume, serves to induce a proportionate flow of gas to form a mixture of predetermined air-gas ratio over a substantial range of supply. The specific construction of this mixer forms no part of the present invention, and therefore is not disclosed herein, but a suitable mixer is disclosed in U. S. Letters Patent No. 1,684,500 granted to G. W. McKee. The mixer 29 is connected through a line 30 to a suitable source of air under pressure, such as a. blower 31, ada ted to be driven by an electric motor 32. as is adapted to be supplied froma suitable source (not shown) through a line `33 to the mixer 29.

The pilot burner 27 is connected through a line 34 to a suitable source of air under ressure." To 'accomplish an object of this invention the source of air under pressure for the pilot burner 27 is entirelyseparate from the source supplying air to the main burner 26, and is adapted to be driven by means separate from the means for driving the source of air for the main burner. In the present instance, the source of air for the pilot burner 27 consists of a blower 35 driven y an electric motor 36. The pilot burner 27 is connected through a branch line/37 to the main gas line 33.

In order that no gas will be delivered tol.-

the mixer 29 unless there is also a suicient supply of air being delivered to the mixer,-

means is provided which is responsive" to the supply of air for controlling the supply of gas. his means comprises a diaphragm valve 38 interposed in the gas line 33 between the line 37 and the mixer 29. It will be evident that the valve 38 does not control the su ply of gas to the pilot burner 27. One si e of the dia hragm chamber of the valve 38 is connecte throu h a line 39 to the line v at the outlet side o the blower 31. When the blower is put into operation, and air is supplied to the line 30, air ressure in the line 39 will open the gas va ve 38 and conversely, when the sup ly of air to the line 30 is stopped, the va ve will close. Thus, no gas w1 be supplied to the burner 261mless a supply of au' to the burner is available.

- In the same manner, means responsive-to the su ply of air to the pilot burner 27 for contro ing the supplyl'vhof gas to! the pilot burner is provided. is means comprises" a dia ra vvalve 40 interposed in the gas line llie side of the diaphragm chamber of the valve 40 is connected throu h a line 05 41 to the line 34 supplying air to t e pilot` ing valve 42. The specific construction of this valve forms no part of the present in- 'I5 vention, and therefore is not disclosed herein, but a suitable valve is disclosed in our co-pending application for U. S. Letters Patent Serial No. 348,793 filed March 21, 1929. Preferably, this valve comprises a valve member in the line 30 and operatively connected to an expansible diaphragm. rlhe interior o the latter is connected 'through a line 43 to the steam space 18 of the Aboiler 10. On arising pressure in the steam space 18, the diaphragm expands serving to close the valve proportionately, but the diaphragm does not permit the valve to close completely. Thus, the supply of air to the burner 26, and hence the supply of fuel mixture,.is automatically regulated in accordance with pressure conditions in the steam space 18.

Suitable control means is provided for operating the; motor 36 drives the'pilot blower 35, said control meansbein eectual to stop the operation of the-motor i the pressure in the gas line 37 to th'e pilot burner 27 falls below a predetermined minimum. This means comprises a suitable ressure oner'ated switch '50, interposed in t e pilot gas sus4 conduit 37 between the diaphragm valve 40 A am'xthe pilot burner 27 The switch 50 is adapted to remain closed as long as the pre's-,l

sure, in the conduit' 37 is above a predetermined minimum but should the pressure .in said conduit fall below this predetermined minimum then the switch will open automati# cally. Reclosing of the switch is accomplished by manual means.

Electric kcurrent for operatin the motor 36 is sup lied through two lea s 44 and 45 connecte rto a suitable starting box 46. The star-tin `box 46 is under the control of a suitable e ectromagnet coil 47. Electric current is supplied to the starting box through two leads 48 and 49 connected respectively to current means L1 and L2.

One end of the electromagnet coil 47 isconl nected to the lead 49. The dtheirend of the electromagnetcoil is connected through a lead53 to one terminal of a manually operated switch 52, the other terminal of :said switch being connected through a lead lfto one terminal .of the switch 50. The-.other terminal of the switch 50v is connected 125 throu h a lead 54 to the lead 48. i ZThus it is seen t at when the switches 50 and 52 are closed there is a complete circuit between the current main L1, lead 48, lead 54, switch 50, lead 51, switch 52, lead 53, electromagnet coil 47, lead49andfthe currentmn S l long as this 'circuit remainscomplte the electromagnet coil`47 operates to maintain the starting box 46 in the closed position permitting current to flow from the mains L1, and L2 to the motor 36. In case the switch 52 should be opened manually or if the switch 50 should `open dueto a fallin gas pressure in the conduit 37, then thecircuit through the electromagnet coil 47 would be broken and consequentlythe startingbox would open, breaking the circuit between thel current mains Lland L2 thus stopping the operation of the motor 36.

Switch 50 is semi-automatic in its operation and is adapted to be manually reset when it is desired to close the circuit control-A ling the motor 36 after the switch has been.

opened automatically due to a fall in gas pressure in the conduit 37. In order to startthe pilot motor 36' it is necessary first to manually reset switch 50 and close the manually operated switch 52 in order to complete the c1rcuit controlling the pilot motor. Switch 50 must be held manually in the closed position until suiiicient air pressure from the blower has been built up in the conduit 34 and conduit 41 thus opening the diaphragm valve admitting gas to the pilot burner and operating to maintain the switch in 'the closed position until the gas pressure in the conduit 37 should once again fall below a predetermined value.

Suitable control means also is provided for controlling the motor 32 driving the main blower 31, said control means bein effectual to stop the operation of the motor i the pressure in the steam space 18 exceeds a predetermined maximum,.if the Water level in the boiler 10 falls below a predetermined minimum, if the starting box switch 46 controlling ithefpilotblower 36 operates to stop the'pilot motor or if it is desired to control the motor 32 manually. In the present instance this motor is represented as a three phase motor and it is connected through leads 55, v56 and P 57 to a suitable starting box 58 under the control of a suitable electromagnet coil 59. The

starting box isconnected through leads 60, 61 and 62 to current mains La, L4, and L5.

A suitable pressure operated switch 63 is provided in communication with the steam space 18 through the-line 43 and a branch line 64. Thel switch 63 operates in such a manner that when the pressure within the steam space is below a predetermined value the switch is closed but if the pressure within the steam space should rise above this-predetermined value the'n the switch will open and when the pressure within the steam space again` falls below the predetermined value the switch will close.

- .Suitable means is provided to control motor 32 in accordance with the water level the boiler 10. In the present instance a openandi-nvjien the water level insaid cham- "ber a ain rises above the predetermined vlevel t e switch will close. Devices for operating electric switches in accordance with water level within chambers are well known in the art and the specific construction forms no .pa-rt of the present invention and hence it is not disclosed.

The'starting box 46 is adapted to control the circuit through three leads and is generally known as a three pole starting box, the three poles being under the control of the electromagnet coil 47, In the present instance two poles of this starting box are used across the power leads 44 and 48, 45 and 49these leads transmitting electric current from the current mains L1 and L2 to the motor 36.` The third pole of this starting box is used in the circuit controllingthe motor 32.

One end of the electromagnet coil 59 is connected to the power lead 60. The other end of the coil being connected through a lead 74 to one terminal of the third pole of the starting box 46. The other terminal of the third pole of the starting box 46 is connected through a lead 73 to a manually operated switch 72. The switch` 72 is connected through a lead 71 to one terminal of the pressure operated switch 63. The other terminal of the pressure operated switch 63 is connected through a lead to one terminal of the switch 68 and the other terminal of the switch 68 is connected through a lead ,69 to the power lead 61. Thus there is a complete Acircuit from the power main Ls through lead 1, y -nof ole of the starting box switch 46, lead switch 72, lead 71, switch 63, lead 70, switch .l

60, electromagnet coil 59, lead-7 4, the third 68, lead 69, lead 61 and power main L4. When the switches 7 2, 63 and 68 are in the closed position and the starting box 46 is closed then motor 32.

To start the system .from a Acold boiler, de-

livery of gas and air to the pilot burner 27 is started y starting the motor 36 as herein previously described. The pilot burner is lighted by means not shown. Since there is .f then no pressure in the steam space 18 and consequently no pressure in the conduit 43 the switch 63 will be in theclosed position and the air regulating valve 42 will be in the fully 115 the circuit is complete permitting electric curair regulating valve 42 to thus reducing the amount of air being dep open position. If the water level in the boiler is above a predetermined minimum the water level in the chamber 65 will also be above a predetermined minimum and consequently the switch 68 will be in the closed position. Then to start the motor 32 it is only necessary to close the manually operated switch 72 and thus complete the control circuit throu h the electromagnet coil 59. Completing t e circuit through the electromagnet coil 59 causes the start-ing box 58 to close and thus the motor 32 and the blower 31 are started.

The blower 31 causes air under pressure to be delivered through the conduit to the mixer 29. Air pressure-from the conduit 30 is transmitted through the conduit 39 to the pressure responsive valve 38 causing said valve to open, thus admitting gas to the mixer 29. The mixture of gas and air is delivered through the conduit 28 to the burner 26 and ignited by the burner 27. As the pressure in the steam space 18 increases the pressure in the conduit 43 also increases causing the partially close livered to the mixer 29 and consequently reducing the amount of mixture of gas and air to the burner 26. If the pressure in the steam space 18 should rise above a predetermined maximum then the switch 63 will open breaking the circuit through the electromagnet coil 59 causing the starting box switch 58 to open, thus the motor 32 and the blower A31 are stopped.

i As soon as the blower 31 is stopped there will then be no air pressure in the conduit 30 and consequently no air pressure in the conduit 39 thus the valve 38 will close preventing any further supply of gas to the mixer 29. When the pressure in the steam space 18 again falls below the predetermined minimum the switch 63 will again close starting the motor 32. -If the pressure in the steam space continues to fall then the air regulating valve 42 will be caused to open in proportion to the drop in pressure, thus increasing the amount of mixture of air and gas being delivered to the burner 26.

In case the water level in the boiler 10 falls Q below a predetermined minimum the water level in the chamber 65 will also fall below the predetermined minimum thus causing the switch 68 to open stopping the motor 32.

Uien the water level in the chamber 65 again rises above the predetermined minimum the switch 68 will close and hence start the motor 32. If it is desired to manually stop the motor 32 is only necessary to open the switch 72. If it is desired to manually stop both motors 32 and 36, it is only necessary to open the switch 52 thus breaking the circuit through the electromagnct coil 47 causing the starting box switch 46 to open, breaking the circuit between the current mains Ll and L2 and the motor 36. Opening of the starting box switch 46 breaks the circuit through the electromagnet coil 59, causing the starting box switch 58 to open, breaking the circuit between the current mains La, L4, and L, and the motor 32.

It is seen that a failure of electric supply to the-motor 32 would cause the blower 31 to stop and thus there would be no air pressure to act on the diaphragm of the valve 38 and it would close preventing any gas from flowing to the main burners 26. In case of a failure of electric supply tothe motor 36 there would be no air pressure lin the conduit 41 and consequently the valve 40 would close shutting oil'l the gas to the pilot burner 27 and o erating to open the switch 50 thus shutting own the entire system until it is manually restarted by resetting switch 50. In any case ot failure of gas supplyv to the conduit 33 the entire system is shut down by means of the switch 50 and even if gas should again be supplied to the conduit 33 no gas would be delivered to the burners 26 or 27 because of the automatic closing of the diaphragm valves 38 and 40 due to the stoppage of the blowers 31'and 35 and motors 32 and 36 which cannot be restarted automatically if the switch 50 is open.

e claim as our invention:

1. A control system for boilers comprising,`

in combination, a main burner, means for supplying air under pressure to said main burner, means 'for supplying fuel to said main burner, a valve means interposed in said last mentioned means and operatively connected to said irst mentioned means to control thesupply of fuel, said valve means being operable to prevent the supply of fuel when said lirst mentioned means is inoperable, a pilot burner, means for supplying air under pressure to said pilot burner, means for supplying fuel to said pilot burner, and a valve means interposed in said last mentioned means and operatively connected to said pilot burner air supply means to control the supply of fuel, said last mentioned valve means of fuel when said pilot burner air supply means is inoperable.

2. A control system. for boilers comprising, in combination, a. burner, a source of air under pressure, a line connecting said source to said burner, a proportional air and gas mixer interposed in said line, a gas supply line connected to said mixer, a pressure responsive valve in said gas line, means for transmitting the pressure of said source to said valve to open the latter, a pilot burner, a second source of air under pressure, a line connecting said second source to said pilot burner, a gas supply line connected to said pilot burner, a pressure responsive valve in said last mentioned gas supply line, means for transmitting the pressure of said second source to said last mentioned valve to open elng operable to prevent the supply the latter, and pressure-operated means controlled by the supply of gas to said pilot burner operable to prevent the supply of air to both burners when the pressure of the gas flowing to said pilot burner falls below a predetermined amount.

3. A control system for boilers comprising, in combination with a boiler adapted to generate steam under pressure, a burner, a source of air under pressure, a line connecting said source to said burner, a pressure responsive valve interposed in said line, means for transmitting the pressure of said boiler to said valve to vary the How of air through said line in accordance with the pressure in said boiler, a proportional air and gas mixer interposed in said line between said burner and said valve, means for supplying gas to said mixer, a pressure responsive valve in said gas line, means for transmitting the pressure from said source to said last mentioned Valve to open the latter, a pilot burner, a second source of air under pressure, a line connecting said second source to said pilot burner, means for supplying gas to said pilot burner, a pressure responsive valve in said last. mentioned means, and means for transmitting the pressure from said second source to said last mentioned valve to open the latter.

4. A control system for boilers comprising, in combination, a main burner, means for supplying air under pressure to said main burner, an electric motor driving said means,'a pilot burner, means for supplying air under pressure to said pilot burner, an electric motor driving said last mentioned means, means for supplying gas to said main burner, means for supplying gas to said pilot burner, and meansoperable to prevent the operation of said first mentioned motor when said second mentioned motor is inoperable.

5. A control system for boilers comprising, in combination, a burner, means for supplying air to said burner, means regulated by the ow of air to said burner to admit gas to said burner, a pilot burner, means for supplying air to said pilot burner, means regulated by the ilow of air to said pilot burner to admit gasto said pilot burner, and means regulated by the tiow of gas to said pilot burner to cut ofi' the flow of air to both burners when the flow of gas to the pilot burner is cut oii. v g

6. A control system for boilers comprising, in combination with a water level boiler, Ia burner, a proportional air and gas mixer, a line connecting said burner with said mixer, a source of-air under pressure, a line connecting said source with said mixer, a pressure responsive valve interposed in said last mentioned line adapted to vary the ow of air through said line in accordance with the pressure in the steam space of said boiler, means for supplying gas to said mixer, a pressure responsive valve interposed in said means, means for transmitting the pressure of said source to said valve adapted to open the latter, an electric motor driving said source, means responsive to the pressure in said boiler adapted to control said motor, means responsivel to the water level in said boiler adapted to control said motor, a pilot burner, a second source of air under pressure, a line connecting said second source to said pilot burner, means tor supplying gas to said pilot burner, a pressure responsive valve i11- terposed in said last mentioned means, means for transmitting the pressure of said second source to said last mentioned valve to open .the latter, an electric motor driving said seeond source, means to cause said last mentioned motor to be inoperative when said last mentioned gas supply meansis inoperative, and means to cause said first mentioned motor to be inoperative when said second mentioned motor is inoperative.

7. A control system for boilers comprising, in combination with a water level boiler, a burner adapted toY burn a. mixture of air and gas, means for supplying air under pressure to said burner, means for supplying gasto said burner, an electric motor drivingl said first mentioned means, means for supplying electric current to said motor, a switch interposed in said last mentioned means, a pilot burner, means for supplying air under pressure to said pilot burner, means for supplying gas to said pilot burner, means for opening said switch when said air supply to said pilot burner is inoperative, means for open-v ing said switch when the pressure in said boiler rises above a predetermined maximum, and means for opening said switch when the water level in said boiler falls below a predetermined minimum.

8. A control system for boilers comprising, in combination, a burner, a source of air under pressure, a line connecting said source to said burner, a proportional-air and gas mixer interposed in said line, a gas supply line connected to said mixer, means operable to open said gas line only when air is being supplied to said mixer, a pilot burner, a second source of air under pressure, a line connecting said second source to said pilot burner, a gas supply line connected to said pilot burner, means operable to open said last mentioned gas supply line only when air is being supplied to f said pilot burner, and means to cause both sources of air under pressure to be inoperable when said pilot burner is inoperable.

In testimony whereof we havey hereunto aixed our signatures.

CHARLES B. PAGE.

ERNEST W. REDDERSON. 

